Magnesium has great interested in the electronic devices and structural parts for the weight reduction, because magnesium is rich resource and the lightest in the structural materials. When magnesium is used as the structural parts, such as in the railcars and automobile, we have to develop high strength, ductility and toughness materials for the satisfaction of reliability and safety. Recently, a wrought process, known as a strain working process, is one of the effective methods to produce the high strength, ductility and toughness in magnesium alloys. For example, wrought materials have superior strength and ductility compared to cast materials, as described with reference to FIG. 15 (Materials Science and Technology, T. Mukai, H. Watanabe, K. Higashi, 16, (2000) pp. 1314-1319). Wrought materials also have superior strength and fracture toughness compared to cast materials, as described with reference to FIG. 16 (Materia, Hidetoshi Somekawa, 47, (2008) pp. 157-160).
However, since magnesium is the hexagonal crystalline structure, the wrought processed materials, which produced by strain working, e.g., rolling and extrusion, have texture, i.e., basal plane is parallel to the processing direction. Therefore, these materials show high tensile strength but low compression strength at room temperature. When the conventional wrought processed magnesium alloys apply to the structural parts, these materials have are very brittle and difficulties to deform in isotropic at the position, where compressive strain occurs. This point is a serious problem.
Recently, a unique phase, called a quasicrystalline phase, that does not have the periodic structure was found to develop in a Mg—Zn-RE (RE: rare earth elements=Y, Gd, Dy, Ho, Er, Tb) alloy.
The quasicrystalline phase is a unique characteristic, i.e., formation of coherent interface. Since the quasicrystal phase and magnesium shows a good lattice matching, the interface between quasicrystal phase and magnesium is very strong. Thus, when the quasicrystal phase is dispersed into the magnesium matrix, these materials resolve the above mentioned issues; reduction of texture and reduction of the yield anisotropy with high strength properties. However, there is a serious problem to form the quasicrystalline phase in magnesium alloy: The essential use of rare earth elements. The rare earth elements are very rare and there is always the risk of price increase, although these materials with addition of rare earth elements show excellent properties.
Specifically, for example, Patent Documents 1 to 3 describe the addition of the rare earth elements (particularly, Y) is necessary to form the quasicrystal phase in magnesium matrix. Patent Document 4 describes the addition of the rare earth elements (Y or other elements) is necessary to form the quasicrystal phase in magnesium matrix. In addition, this document shows that the grain refinement of matrix and the dispersion of quasicrystal phase lead to the reduction of yield anisotropy. The publication also describes the secondary formability conditions, such as temperature and speed, of the magnesium alloy with dispersion of quasicrystal phase particle. However, the problem is still remained; the additional rare earth element is necessary, same as all of these publications.
Meanwhile, there are some reports; a different approach that does not make use of rare earth elements. For example, Non-Patent Documents 1 and 2 describe the formation of Mg—Zn—Al quasicrystalline phase. However, since the quasicrystal is the only single crystal, the Mg matrix is absent. Non-Patent Document 3 shows that the size of Mg matrix is 50 μm or more than 50 μm because of the casting process. These publications thus do not describe exhibiting the high-strength, high-ductility, and high-toughness properties comparable to or superior to those by the addition of rare earth elements. In addition, it is also considered technically difficult to obtain such properties.    Patent Document 1: JP-A-2002-309332    Patent Document 2: JP-A-2005-113234    Patent Document 3: JP-A-2005-113235    Patent Document 4: WO2008-16150    Non-Patent Document 1: G. Bergman, J. Waugh, L. Pauling: Acta Cryst. (1957) 10 254.    Non-Patent Document 2: T. Rajasekharan, D. Akhtar, R. Gopalan, K. Muraleedharan: Nature. (1986) 322 528.    Non-Patent Document 3: L. Bourgeois, C. L. Mendis, B. C. Muddle, J. F. Nie: Philo. Mag. Lett. (2001) 81 709.